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Dark brown stools can be suggestive of gastrointestinal bleeding
or infection .
Since your child is having persistent fever despite paracetamol therapy it needs to be investigated so that diagnosis can be confirmed and appropriate treatment ( antibiotics course etc ) can be started .
Please take your child to a pediatrician
for a thorough evaluation promptly and avoid use of paracetamol without prescription as the dose should be calculated as per weight and age by a doctor to avoid sideeffects like liver damage
Meanwhile make sure to give your child plenty of water and a multivitamin
and zinc supplement
and probiotics to ensure faster recovery.
Wishing your child a speedy recovery.